1. Field of the Invention
The present invention relates to carrier rapier used in a both-side rapier loom or in a one-side rapier loom.
2. Description of the Related Art
In general, weft insertion in a both-side rapier loom is performed with an insert rapier, provided at a yarn feeding side, and a carrier rapier, provided at a side opposite to the yarn feeding side. A weft, provided consecutively with a weft supply package, has an end thereof held by the insert rapier, and is conveyed to a weaving width center in a warp shed. At this position, the weft is received by the carrier rapier inserted in the shed from a side opposite to a weft insertion side, and is conveyed up to the side opposite to the weft insertion side of a cloth.
For example, as a structure of the carrier rapier in the both-side rapier loom, a structure in which a weft is naturally transferred by a movement relative to the insert rapier is available (refer to, for example, Japanese Unexamined Patent Application Publication No. 57-77353). A related carrier rapier of this type includes a carrier head, having a hook (what is called a turn-back portion in the application) provided at one end, and a moving wedge portion (what is called a catch lever in the application), disposed at an inner side of the hook so as to contact an inwardly facing surface of the hook. A wedge-shaped gap capable of holding a weft is formed between the inwardly facing surface of the hook (what is called a base surface in the application) and an opposing surface opposing the moving wedge portion.
In the carrier rapier, the hook and the moving wedge portion are such that the wedge-shaped gap becomes gradually and continuously smaller towards a tip of the carrier head, so that they eventually contact each other. Accordingly, a weft guiding portion that gradually widens from the wedge-shaped gap is formed at a side closer to a tip of the hook than the wedge-shaped gap. The moving wedge portion is biased so as to press the inwardly facing surface of the hook with, for example, a spring.
Near the weaving width center, when the carrier rapier receives the weft from the insert rapier, retreating of the carrier rapier relative to the insert rapier causes the wedge to be guided to the weft guiding portion (formed by the moving wedge-shaped portion and the inwardly facing surface of the hook of the carrier rapier) and to be held so as to be moved into a location (what is called a wedge holding portion in the application) in a gap capable of holding the weft. (Here, this type of wedge holding portion is called a negative weft holding device). In this way, after the weft is partly held at the location with which it contacts in the wedge-shaped gap in the carrier rapier, the weft is inserted to the side opposite to the weft insertion side by travelling of the carrier rapier.
In contrast, weft insertion in a one-side rapier loom is performed with a rapier head provided at a side opposite to a yarn feeding side. The rapier head is first conveyed in a direction opposite to a weft insertion direction in a warp shed. Then, the rapier head receives a laid weft at a position situated closer to a weft supply package than a weaving width, and is conveyed in an opposite direction (weft insertion direction) in the warp shed. In the application, not only the receiving side carrier rapier in the both-side rapier loom, but also such a rapier head provided at the side opposite to the yarn feeding side in the one-side rapier loom will hereunder be called a “carrier rapier.”
However, there are a wide variety of types of wefts. In particular, when a weft whose portions have a low degree of alignment as a whole, such as a multi-filament yarn (formed of a plurality of filaments), a zero twist filament yarn (soft twisted filament yarn), or a an unsized yarn, is used, the portions of the weft diverge at a portion where the weft is held by the carrier rapier until the time the weft is inserted to a weaving end at the side opposite to the yarn feeding side by the carrier rapier (see FIG. 21).
Therefore, weft tension is concentrated at a portion that is adequately held by the weft holding portion (that is, a filament held at the contact portion where the gap is small) among the portions of the entire weft guided to the weft guiding portion. Therefore, for example, the weft is torn or the filament held at the back portion of the gap is broken or bent, thereby damaging the weft. As a result, the quality (related to the defects and texture of the weft) of a cloth is impaired.
The inventor of the application considers that the size of the gap formed by the base surface and the opposing surface and extending to the weft holding portion significantly affects the divergence of the portions of the weft. The following points will be described in detail.
In the related carrier rapier, when the wedge-shaped gap is seen from its side, the base surface and the opposing surface have linear shapes, have gently curved shapes, or have shapes that are a combination of these. For example, when the base surface and the opposing surface have gently curved shapes, the carrier rapier is formed so that its shape changes from a gently curved shape to a linear shape from a base end to a tip of the carrier rapier.
When both of the base surface and the opposing surface have linear shapes, an angle formed by the base surface and the opposing surface becomes constant (this angle is hereunder referred as “formation angle”). When at least one of the base surface and the opposing surface has a curved shape, the formation angle is gradually reduced towards the tip of the carrier rapier. Therefore, a formation angle at the weft guiding portion is a value that is at least greater than or equal to a formation angle at the weft holding portion.
The rate by which the size of a gap extending from the weft guiding portion to the weft holding portion is reduced is proportional to the formation angle. Therefore, the rate by which the size of the gap at the weft guiding portion is reduced is also gradually reduced in proportion to the formation angle.
A weft is guided to such a weft guiding portion and is held so as to be moved into the weft holding portion having a gap that has a size allowing the weft to be held. However, as seen from the weft holding portion, the gap at the weft guiding portion has a size that increases in proportion to the formation angle that is gradually increased. Therefore, when the weft reaches the weft holding portion, it cannot be said that the weft adequately contacts the base surface and the opposing surface at the weft guiding portion. In particular, when the portions of the weft have a low degree of alignment, the weft reaches the weft holding portion while its portions have a low degree of alignment.
The weft whose portions have a low degree of alignment is a weft that tends to be in a state in which a large number of spaces is formed between filaments constituting the weft as seen in cross section. When the weft in this state reaches the weft holding portion, the ratio of filaments that are inadequately held as a result of not being moved into the weft holding portion among the large number of filaments constituting the weft becomes large. In such a weft whose portions have a low degree of alignment, a holding force (that is, a friction force) acts upon only some of the filaments that are disposed at the gap at the weft holding portion and excessively moved into the weft holding portion. However, this holding force barely acts upon the filaments that are not adequately moved into the weft holding portion.
In addition, when the carrier rapier that has received the bulky weft travels towards the side opposite to the yarn feeding side, the weft tension is increased as a result of, for example, the weft contacting a shed warp. Therefore, the filaments upon which the holding force does not act (that is, the filaments that are not adequately moved into the weft holding portion) are pulled towards the yarn feeding side. As a result, the filaments of the weft at this portion diverge, thereby causing the weft to be torn in the worst case. Comparatively speaking, the tension of the entire weft concentrates on the filaments that are moved in excessively, thereby causing the filaments to be torn or bent at this portion. When the filaments are diverged once in this way, they are not aligned they were originally. When such a weft whose tension between the filaments is not uniform is woven, weaving detects, such as what is called a weft defect, occurs. As a result, the quality of a cloth is considerably deteriorated.
In order to prevent such defects from occurring, the formation angle may be reduced to make as small as possible the gap at the weft guiding portion, in particular, the gap near the weft holding portion. In this case, the base surface and the opposing surface need to be long so that the gap (opening) of the entrance of the weft guiding portion is a certain size. However, there is a limit as to how long they can be made because there is a limit as to how large the overall size of the carrier rapier can be made.